Private circuit provision in a telecommunications network

ABSTRACT

A telecommunications network includes local switches, main switches and access lines. A switching unit which takes the form of a computer with switching capability is connected to the local switch on a 30 channel ISDN link. In order to form a private circuit between two access lines, the following operations are performed. At local switches, access line are physically connected to free local switch lines. At each of the local switches, an engineer uses the free local switch line which has just been connected to an access line to make a call to the switching unit. The switching unit captures the CLI of this local switch line. The engineer then enters an identifier for the private circuit which is to be formed and instructs the switching unit to form a private circuit. The switching unit then calls these two free local switch lines and then forms the private circuit by connecting the local switch lines together within itself.

RELATED APPLICATION

This application is related to copending commonly assigned applicationSer. No. 09/043,420 filed Mar. 19, 1998.

BACKGROUND OF THE INVENTION

This invention relates to a method of providing a private circuit in atelecommunications network which has at least two local switches, eachlocal switch having a group of local switch lines and being associatedwith a group of access lines. The invention is also concerned with sucha network which is arranged to provide a private circuit.

Related Art

In the usual method of providing a private circuit between first andsecond access lines, physical connections are made by engineers atappropriate exchange buildings so as to provide the private circuit.Where a failure occurs in the private circuit in the network, it is ausual requirement to restore the private circuit quickly. There is alsosometimes a requirement to provide a private circuit quickly. Thisinvention is concerned with the quick provision or restoration of aprivate circuit.

A known method of providing quick provision or restoration of a privatecircuit between a first access line associated with a first local switchand a second access line associated with a second local switch is asfollows. At the first local switch, an engineer connects the firstaccess line to a first local switch line. A second engineer thenconnects the second access line to a second local switch line at thesecond local switch. The two engineers then instruct network managementpersonnel to provide a permanent switched circuit between the first andsecond local switch lines through appropriate switches in the network.This known method suffers from the disadvantage that it involves networkmanagement personnel so it tends to be laborious and time consuming.

SUMMARY OF THE INVENTION

EP-A-0 400879 describes a dynamic shared facility system for privatenetworks.

According to one aspect of this invention, there is provided a method ofproviding a private circuit in a telecommunications network, saidnetwork having at least two local switches and a switching unit, eachlocal switch having a group of local switch lines and being associatedwith a group of access lines, said method comprising the steps of:

physically connecting a first access line to a first local switch lineat a first local switch;

physically connecting a second access line to a second local switch lineat a second local switch;

instructing said switching unit to form a connection between said firstand second local switch lines;

said switching unit calling said first local switch line;

said switching unit calling said second local switch line; and

said switching unit forming a connection between said first and secondlocal switch lines with itself so as to form a private circuit betweensaid first and second access lines.

In comparison with the known method of quick provision or restoration ofa private circuit, the method of the invention has the advantage that itdoes not involve network management personnel. Consequently, the privatecircuit can be provided more quickly.

According to a second aspect of this invention there is provided atelecommunications network having at least two local switches and aswitching unit, each local switch having a group of local switch linesand being associated with a group of access lines, each access linebeing connectable to a local switch line, said switching unitcomprising:

means for receiving an instruction to form a connection between a firstlocal switch line and a second local switch line to form a privatecircuit; and

means for forming a connection between a first local switch line and asecond local switch line within itself to form a private circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

This invention will now be described in more detail, by way of example,with reference to the drawings in which:

FIG. 1 is a block diagram of a telecommunications network embodying thisinvention;

FIG. 2 is a block diagram of a local switch and an associateddistribution frame located at an exchange building and forming part ofthe network of FIG. 1;

FIG. 3 is a block diagram of a switching unit forming part of thenetwork of FIG. 1;

FIGS. 4A-4C provide a flow chart of the steps which are used to providea private circuit in the network of FIG. 1 using the switching unit inone embodiment of this invention;

FIG. 5 is a flow chart of the steps which are used in the network ofFIG. 1 to disconnect a private circuit which has been formed using theswitching unit; and

FIGS. 6A-6C provide a flow chart of the steps which are used to providea private circuit in the network of FIG. 1 using the switching unit inanother embodiment of this invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring now to FIG. 1, there are shown some of the components of apublic telecommunications network. As shown in FIG. 1, these componentsinclude four fully-interconnected main switches 10, 11, 12, 13 and threelocal switches 14, 15, 16. Each switch is located at a respectiveexchange building.

The local switches 14, 15 and 16 are connected, respectively, to mainswitches 10, 11 and 13. For reasons of simplicity, FIG. 1 shows onlyfour main switches and three local switches. However, in a typicalpublic telecommunications network there would be a much larger number ofboth main switches and local switches. For example, BT's UK publictelecommunications network has more than 60 main switches.

Each of the local switches is associated with a group of access lines,typically several thousand access lines. Each access line is formed froma pair of copper wires and the end of each access line which is remotefrom the associated local switch is connected to terminal equipmentbelonging to a user of the network. Some of the access lines 20, 21associated with local switches 14, 15 are illustrated in FIG. 1.

The public telecommunications network shown in FIG. 1 is capable ofproviding both switched connections and private circuit connectionsbetween access Fines. The switched connections are formed, in a wellknown manner, by using the switching capabilities of the local and mainswitches. A private circuit between two access lines at different localswitches is normally created by making physical connections at exchangebuildings lying on a path which connects the two access lines. As willbe described in more detail below, the network shown in FIG. 1 alsoprovides an alternative and faster method of providing a private circuitbetween two access lines which are associated with two different localswitches. In this method, the private circuit is formed without makingphysical connections at exchange buildings between the two switchesassociated with the access lines.

This alternative method is useful where a private circuit is required atvery short notice or where it is required to restore a private circuitquickly after a fault has occurred.

The network of FIG. 1 also includes a switching unit 25 and anassociated computer 26. The switching unit 25, as will be described indetail below, is used in the alternative method of providing a privatecircuit.

The network of FIG. 1 also includes a service management system 28 whichtakes the form of a computer. The service management system 28 receivesorders and fault reports from users of the network. Although not formingpart of the present invention, and not illustrated in FIG. 1, theservice management system 28 is capable of sending instructions to theswitches to provide circuits to meet orders from the users of thenetwork and also to take appropriate action to correct faults.

Each of the switches 10 to 13 and 14 to 16 shown in FIG. 1 is a System Xswitch manufactured by GEC Plessey Telecommunications Ltd. The maincomponents of a local switch 14 are illustrated in FIG. 2 and thesecomponents will now be described.

Referring now to FIG. 2, the local switch 14 is located at an exchangebuilding indicated by a dashed line 15. At the exchange building 15,each of the access lines 20 is connected to a respective terminal on theinput side of a distribution frame 30. The switch 14 includes a bank ofline cards 31. The input terminal of each line card is connected to arespective terminal on the output side of the distribution frame 30. Theoutput terminals of the line card 31 are connected to input terminals ofa concentrator 32 and the output of concentrator 32 is connected to aprocessor 33.

The input terminals of the line cards 31 represent the inputs to thelocal switch lines of the local switch 14. In order to connect one ofthe access lines 20 to a local switch line, a physical connection ismade between the terminal on the input side of the distribution frame 30to which the access line is connected and one of the terminals on theoutput side of the distribution frame 30.

In the present example, the switching unit 25 is implemented as acomputer provided with switching capability.

Referring now to FIG. 3, the components of switching unit 25 comprise acentral processing unit (CPU) 40, a video display unit (VDU) 41, akeyboard 42, input/output ports 43, a switch processor 44 which providesthe switching capability, a store 45 and signal processing cards 46. Thesignal processing cards include a speech synthesiser card, a dual tonemulti-frequency detector card and a dual tone multi-frequency generatorcard. The input/output ports 43 connect the switching unit 25 to thelocal switch 16 via a 30 channel integrated services digital network(ISDN) communications link and also to computer 26.

The store 45 is formed from hard disk memory, read only memory (ROM) andrandom access memory (RAM). The store 45 contains the program forcontrolling the switching unit 25.

A switching unit of the type shown in FIG. 3 is available from Aculabplc of Lakeside, Bramley Road, Mount Farm, Milton Keynes under the nameMillennium Conn.

As will be described in more detail below, in order to provide a privatecircuit between two access lines, for example one of the access lines 20and one of the access lines 21, each of the access lines is connected atits local switch to a local switch line. The local switch lines are thenconnected to each other via the switching unit 25. One embodiment of theseries of operations which are used to provide a private circuit willnow be described with reference to FIGS. 4A-4C.

In this embodiment, when a decision is made to create a private circuit,details of the private circuit to be formed including identifiers forthe access lines which are to be connected and an identifier for theprivate circuit are entered in the service management system 28. Theservice management system 28 supplies the identifier for the privatecircuit and identifiers for the two access lines to the computer 26.

Then, a first engineer makes a physical connection between the firstaccess line and a first local switch line at the local switch for thataccess line. A second engineer makes a physical connection between thesecond access line and a second local switch line at the local switchline for that access line.

Next, in step 50, the first engineer calls the switching unit 25 on thefirst local switch line. He may do this either by dialling the fulltelephone number of the switching unit 25 or by dialling a short codewhich is translated in the local switch to the full telephone number.

In the telecommunications network shown in FIG. 1, the calling lineidentity (CLI) of a calling local switch line is transmitted at thebeginning of each call to the called line. The calling line identity isalso transmitted in the signalling channel of a 30 channel ISDN link.Thus, at the beginning of a call, terminal equipment attached to the endof a single line or the end of a 30 channel ISDN link can retrieve thecalling line identity of the calling line. In step 51, the switchingunit 25 captures the CLI of the first local switch line.

The switching unit 25 then transmits a speech message to the first localswitch line inviting the engineer to enter his personal identificationnumber (PIN). In step 52 the first engineer enters his PIN on hishandset.

The switching unit 25 then transmits a speech message to the first localswitch line inviting the engineer to enter the identifier for theprivate circuit. The engineer then enters the identifier in a step 53.

Then, the switching unit 25 transmits a speech message to the firstlocal switch line inviting the engineer to choose between circuitprovision and circuit termination. For each option, it specifies a digitwhich is to be entered which may be, for example, "one" for circuitprovision and "two" for circuit termination. Then, in a step 54, theengineer enters the digit for circuit provision.

The switching unit 25 then transmits a speech message to the first localswitch line confirming the details which have been received and invitingthe first engineer to enter a digit to indicate his agreement with thedetails. In step 55, the first engineer enters this digit. Then, in step56, the first engineer hangs up.

The second engineer then performs a similar series of operations.Specifically, in step 57, the second engineer calls the switching unit25 on the second local switch line. In step 58, the switching unit 25captures the CLI of the second local switch line.

In step 59, the second engineer enters his PIN. In step 60, the secondengineer enters the identifier for the private circuit which is to becreated. In step 61, the second engineer chooses circuit provision and,in step 62, the second engineer confirms the details of the request fora private circuit. In step 63, the second engineer hangs up.

The switching unit 25 then asks the computer 26 to verify that theidentifier for the private circuit which it has received from the firstand second engineers corresponds to an identifier for a private circuitwhich the computer 26 has received from the service management system28. If the identifier is verified, the switching unit 25 calls the firstlocal switch line in a step 64 and the second local switch line in astep 65. As a result of performing steps 64 and 65, the switching unit25 has formed a connection to each of the first and second local switchlines. Two ISDN channels are used for each connection.

Lastly, in a step 66, the switching unit 25 forms a connection withinitself between the first and second local switch lines. As a result ofdoing this, a private circuit is formed between the first and secondaccess lines.

As may be readily appreciated, when a private circuit is formed usingthe steps set out in FIGS. 4A-4C, the private circuit may be createdvery quickly.

The series of operations which are used to terminate a privateconnection formed through the switching unit 25 are shown in FIG. 5 andthese will now be described.

In order to terminate a private circuit, initially an engineer calls theswitching unit 25 in a step 70. Then, in a step 71, the switching unit25 captures the CLI of the calling line. In step 72, the engineer entershis PIN and, in step 73, the engineer enters the identifier for theprivate circuit which is to be terminated.

The switching unit 25 then issues a speech message to the engineerinviting him to choose circuit provision or circuit termination andspecifies a digit which is to be entered for each option. In step 74,the engineer enters the digit for circuit termination.

The switching unit 25 then issues a speech message to the calling linesetting out the details of the request to terminate a private circuitand asking the engineer to enter a specified digit to confirm therequest. In a step 75, the engineer enters this digit and, in step 76,the engineer hangs up.

Then, in step 77, the switching unit 25 breaks the termination withinitself between the first and second local switch lines which have beenused to form a connection. It then terminates its call to each of theselocal switch lines. The switch lines are then physically disconnectedfrom the first and second access lines by engineers in the relevantlocal exchange buildings.

The switching unit 25 sends details of the private circuits which itconnects and disconnects to the computer 26. Specifically, afterconnecting first and second local switch lines together in steps 66, theswitching unit 25 informs the computer 26 of the time of connection, theidentifier for the private circuit and the telephone numbers of thefirst and second local switch lines. After disconnecting first andsecond local switch lines in step 77, it informs the computer 26 of thetime of disconnection, the identifier for the private circuit and thetelephone numbers of the first and second local switch lines. Asmentioned above for each private circuit, the computer 26 receivesidentifiers for the first and second access lines together with theidentifier for the private circuit from the service management system28.

The operator of computer 26 can then use the details logged in computer26 to manage the provision of private circuits using the switching unit25. In general, a private circuit formed using switching unit 25 will bemaintained only until it is possible to replace it with a privatecircuit which is created by forming physical connections in the switchesalong a path between the two access lines which are to be connected.

As mentioned above, the switching unit 25 is connected to the localswitch 16 by a 30 channel ISDN link. Consequently, the switching unit 25may used to provide fifteen 64 kilobit/s private circuits. If it isdesired to use it to provide a greater number of 64 kilobit/s privatecircuits, this may be achieved by providing additional 30 channel linksbetween local switch 16 and switching unit 25. If it desired to use theswitching unit 25 to provide 30 channel ISDN private circuits, this maybe achieved by providing a 30 channel ISDN link between local switch 25and switching unit 25 for each such private circuit.

An alternative embodiment of the series of operations which are used toprovide a private circuit will now be described with reference to FIGS.6A-6C.

In this embodiment, when a decision is made to create a private circuit,in a step 100, the first and second local switch lines are preselectedby the service management system 28. The service management system alsocreates an authorisation code or identifier for the private circuit. Thenumbers of the preselected first and second local switch lines and theauthorisation code are sent to the first and second engineers at thefirst and second local switches. The service management system alsosupplies the numbers of the first and second local switch lines and theauthorisation code to the computer 26 for use by the switching unit 25.

Next, in a step 101, the first engineer connects the first access lineto the first local switch line. Then, in a step 102, the first engineercalls the switching unit 25 on the first local switch line.

In a step 103, the switching unit captures the CLI of the first localswitch line and checks its validity. If it is not valid, the switchingunit clear down the line. If the CLI is valid, in a step 104 theswitching unit 25 ask the first engineer to enter the authorisationcode. In a step 105, the first engineer enters the authorisation codeand the switching unit 25 checks its validity. If the authorisation codeis not valid, the switching unit clears down the line. If theauthorisation code is valid, the switching unit informs the firstengineer that the details of the first leg of the private circuit areconfirmed and it invites the first engineer to hang up. The firstengineer hangs up in a step 106.

In a series of steps 107 to 112, the second engineer performs a seriesof operations which are similar to the operations performed by the firstengineer and described with reference to steps 101 to 106.

Then, the switching unit 25 calls the first local switch line in a step113 and the second local switch line in a step 114. Lastly, in a step115, the switching unit forms a connection within itself between thefirst and second local switch lines, thereby forming a private circuitbetween the first and second access lines.

In this embodiment, in order to terminate a private circuit, the servicemanagement system 26 instructs the switching unit 25 to terminate theprivate circuit. On receipt of such an instruction, the switching unitbreaks the connection within itself between the first and second localswitch lines and then terminates its call to each of the local switchlines.

What is claimed is:
 1. A method of providing a private circuit in atelecommunications network, said network having at least two localswitches and a switching unit, each local switch having a group of localswitch lines and being associated with a group of access lines, saidmethod comprising the steps of:physically connecting a first access lineto a first local switch line at a first local switch; physicallyconnecting a second access line to a second local switch line at asecond local switch; instructing said switching unit to form aconnection between said first and second local switch lines; saidswitching unit calling said first local switch line; said switching unitcalling said second local switch line; and said switching unit forming aconnection between said first and second local switch lines with itselfso as to form a private circuit between said first and second accesslines, wherein said step of instructing said switching unit to connectsaid first and second access lines comprises the steps of:a first usercalling said switching unit on said first local switch line; saidswitching unit capturing the calling line identity of said first localswitch line; a second user calling said switching unit on said secondlocal switch line; and said switching unit capturing the calling lineidentity of said second local swithc line.
 2. A method as in claim 1wherein said step of instructing said switching unit to connect saidfirst and second access lines further comprises the steps of:said firstuser entering an identifier for said private circuit on said first localswitch line; and said second user entering said identifier for saidprivate circuit on said second local switch line.
 3. A method ofproviding a private circuit in a telecommunications network, saidnetwork having at least two local switches and a switching unit, eachlocal switch having a group of local switch lines and being associatedwith a group of access lines, said method comprising the stepsof:physically connecting a first access line to a first local switchline at a first local switch; physically connecting a second access lineto a second local switch line at a second local switch; instructing saidswitching unit to form a connection between said first and second localswitch lines; said switching unit calling said first local switch line;said switching unit calling said second local switch line; and saidswitching unit forming a connection between said first and second localswitch lines with itself so as to form a private circuit between saidfirst and second access lines; wherein said step of instructing saidswitching unit to connect said first and second access lines comprisesthe steps of:a first user calling said switching unit on said firstlocal switch line; said switching unit capturing the calling lineidentity of said first local switch line; said first user entering anidentifier for said private circuit on said first local switch line; asecond user calling said switching unit on said second local switchline; said switching unit capturing the calling line identity of saidsecond local switch line; and said second user entering said identifierfor said private circuit on said second local switch line.
 4. A methodas claimed in claim 3, comprising the further steps of:said first userentering a request to provide a private circuit; and said second userentering a request to provide a private circuit.
 5. A method as claimedin claim 3, comprising the further steps of:preselecting said first andsecond local switch lines; after capturing the calling line identity ofthe first local switch line, said switching unit checking its validity;and after capturing the calling line identity of the second local switchline, said switching unit checking its validity.
 6. A method ofdisconnecting a private circuit which has been provided by the method ofany one of the preceding claims, said method comprising the steps of:auser calling said switching unit; said user entering an identifier forsaid private circuit; said user entering a request for disconnection ofsaid private circuits; and said switching unit breaking the connectionwithin itself between said first and second local switch lines.
 7. Atelecommunications network having at least two local switches and aswitching unit, each local switch having a group of local switch linesand being associated with a group of access lines, each access linebeing connectable to a local switch line, said switching unitcomprising:means for receiving an instruction to form a connectionbetween a first local switch line to a second local switch line to forma private circuit; means for calling a first local switch line; meansfor calling a second local switch line; and means for forming aconnection between a first local switch line and second local switchline within itself to form a private circuit, wherein said means forreceiving an instruction comprises:means for receiving a call on a firstlocal switch line; means for capturing the calling line identity of saidfirst local switch line; means for receiving a call on a second localswitch line; and means for capturing the calling line identity of saidsecond local switch line.
 8. A telecommunications network as in claim 7wherein said means for receiving an instruction further comprises:meansfor receiving an identifier for a private circuit on said first localswitch line; and means for receiving said identifier for said privatecircuit on said second local switch line.
 9. A telecommunicationsnetwork having at least two local switches and a switching unit, eachlocal switch having a group of local switch lines and being associatedwith a group of access lines, each access line being connectable to alocal switch line, said switching unit comprising:means for receiving aninstruction to form a connection between a first local switch line to asecond local switch line to form a private circuit; means for calling afirst local switch line; means for calling a second local switch line;and means for forming a connection between a first local switch line anda second local switch line within itself to form a private circuit,wherein said means for receiving an instruction comprises:means forreceiving a call on a first local switch line; means for capturing thecalling line identity of said first local switch line; means forreceiving an identifier for a private circuit on said first local switchline; means for receiving a call on a second local switch line; meansfor capturing the calling line identity of said second local switchline; and means for receiving said identifier for said private circuiton said second local switch line.